Dynamoelectric machines such as motors typically include a rotatable rotor and a shaft extending outwardly from at least one end of the rotor. The shaft is mounted to the rotor so that the rotation axis of the shaft is coaxial with the axis of rotation of the rotor. The shaft extends from the rotor and through an opening formed in the motor end plate. Typically, a bearing is mounted in the end plate and supports the shaft.
Alignment between the shaft and the bearing is important because any misalignment could disturb operation of the motor, including even possibly rendering the motor inoperable. For example, in normal operation, a hydrodynamic lubrication film is formed between the bearing and the shaft by oil supplied from an oil wick. If side forces or other forces cause misalignment between the bearing and the shaft, the film could be disrupted. As a result, metal-to-metal contact may be made between the bearing and the shaft. Such metal-to-metal contact, of course, is highly undesirable.
Various self-aligning bearing constructions are used to support rotor shafts, including constructions wherein a self aligning bearing having a partial spherical outer surface is located in spherical surface-to-surface seating contact with a bearing seat. A disadvantage of such known spherical surface-to-surface bearing constructions, however, is that the manufacturing tolerances for the spherical bearing surface and bearing seat must be small and thus can be difficult and expensive to achieve. For example, in one method of manufacture, the partial spherical surface on the alignable bearing is made predeterminedly dimensionally greater than that on the receiving surface and a wear-in operation is employed. More particularly, the partial spherical surface on the alignable bearing is oscillated with a preselected force against the mating spherical surface until desired engagement or fit is attained. This wear-in operation is time consuming and costly. Further, materials of low wear resistance are sometimes used to facilitate the wear-in operation, which materials can also lower the wear resistance of the finished assembly.
Other known bearing constructions include, for example, a bearing seat having a partial toroidal surface for seating in a generally circular line of engagement with a bearing surface. These known constructions, however, are complex to design and machine.
Accordingly, it is desirable and advantageous to provide a self-aligning bearing assembly which may be mounted in the motor end plate and which does not have close manufacturing tolerances. It also is desirable and advantageous to provide such a bearing assembly configured so as to minimize forces which normally tend to cause misalignment between the shaft and the bearing.
An object of the present invention is to provide an improved bearing construction which utilizes a generally circular line of seating engagement between a bearing member and a bearing seat but which does not require manufacturing the bearing member and bearing seat to close dimensional tolerances to achieve such seating engagement.
Another object of the present invention is to provide an improved bearing construction which distributes side forces and other forces acting to misalign the bearing and the rotor shaft so as to prevent disruption of the hydrodynamic lubricating film existing between the bearing and the shaft.
Yet another object of the present invention is to provide an improved bearing construction which better retains lubricating oil between the bearing and the rotor shaft.
Still yet another object of the present invention is to provide an improved self-aligning bearing assembly which is economical to manufacture and easily assembled.